Nice weather, we’re having. Mustn’t grumble. Turned out nice again. According to Roland Emmerich, all such pleasantries about the weather are about to become redundant. We British are going to be especially out of luck because we’ll all have frozen to death, as stiff as our own upper lips.

In his latest disaster movie, Herr Emmerich gives himself yet another chance to stereotype every race on earth except the Germans. The Brits, whether white (Ian Holm) or black (Adrian Lester), are dignified, doomed losers to a man. The Japanese, who don’t even get important speaking parts, are panicky when things are dropped on them (maybe it’s something to do with Hiroshima).

The Americans, except for the ones who are picturesquely slaughtered, are gallant survivors or guys who sacrifice themselves so that others may live. This is a director who really knows how to crawl to a US audience.

And rest assured that Emmerich’s flair for massive product placement remains unmatched. You may be able to guess this is a 20th Century Fox movie from the number of times characters tune in exclusively to Murdoch channels in order to find out what’s really going on.

Say what you like about Roland, but when he’s got a recipe for success, he sticks to it. In Independence Day, an American scientist helped save the world from invading space aliens who had levelled Manhattan. In Godzilla, another American scientist rescued the world from a gigantic lizard that was the product of French nuclear testing in the South Pacific, but for some reason travelled half way round the world to vent his outrage on, yes, Manhattan.

Now, in The Day After Tomorrow, a third American scientist (this time, it’s Dennis Quaid) tries to save the world from weather disasters caused by global warming. But he fails early on because of political obstructionism from the US vice-President, and spends the rest of the movie trying to rescue his son (Jake Gyllenhaal), a fourth American scientist in the making, from freezing to death in, forgive me if you’ve heard this before, Manhattan.

If this storyline sounds lame, it is. It’s hard to discern what Quaid’s adventure is going to achieve, except a few action thrills, as he puts two co-workers’ lives at risk in trekking through worse-than-blizzard conditions from Washington DC to New York City merely to keep an appointment with a grown-up son who appears perfectly capable of surviving without him.

And don’t get me started about the would-be tear-jerking sub-plot where Quaid’s doctor wife (Sela Ward) risks her own neck in order to stay with a child cancer-victim who’s reading Peter Pan and plaintively wondering if he too will never grow up. If you get a lump in your throat while watching these scenes, it could be your gorge rising.

The film is terribly devoid of dramatic conflict. Whereas in Troy, there was no one to root for, here there’s no one to root against. The principal bad guy is… the weather.

Emmerich is as eager as Michael Moore to point an accusing finger and swing wild punches at the Bush administration. But even the stupidly obstructionist vice president in The Day After Tomorrow (who looks a lot like the real one, Dick Cheney) is won over to the Green Movement by the end of the movie.

The characterisation makes that in Twister seem deep, and the dialogue is as cheesy as any fan of bad movies could desire.

Dennis Quaid is a fine actor, but not even he can get his mouth around lines like “I think we’ve hit a critical desalinisation point” without raising a smirk. And the entire scene where he solemnly explains the relationship between the Gulf Stream and the world's climate to a room full of meteorological experts is one of several unintentional hoots.

The reason this movie is worth seeing is, quite simply, the action and special effects. The tidal waves, tornados and snowstorms are easily the best ever. The parts of this movie which are thrilling are the destruction of LA by multiple tornadoes and the drowning of Manhattan under giant snowdrifts. Emmerich may not be much cop at story, characters or dialogue, but he’s terrific at destroying America. Osama bin Laden must be green with envy.

However, The Day After Tomorrow must be judged not only as a special-effects movie, but as Science Fiction. And if the fiction is weak, the science is pathetic.

Emmerich exaggerates even the wackiest predictions of the Ecology movement. He got the idea from a book The Coming Global Superstorm, written by Art Bell and Whitley Strieber; and anyone who saw Christopher Walken’s hilariously loopy performance as Mr Streiber in the film Communion (based on Whitley’s claim that he was once abducted by aliens who then sexually molested him) will know how much salt they should take with anything he writes.

More reliable scientific experts assure us that global warming won’t hugely affect countries such as the UK or North America – indeed it may make northern latitudes considerably better places to live – and that the shutting down of the Gulf Stream is a very remote possibility.

According to Carl Wunsch, a leading expert in ocean-circulation systems writing recently in Nature magazine: "The only way to produce an ocean circulation without a Gulf Stream is either to turn off the wind system, or to stop the Earth's rotation, or both... The occurrence of a climate state without the Gulf Stream any time soon — within tens of millions of years — has a probability of little more than zero."

The most adverse effects of global warming, if it turns out to exist, will be not on downtown Manhattan but on tropical, third-world countries, which will have to deal with fierce heat, unpredictable rainfall and higher sea-levels that are likely to cause terrible flooding. Indeed, the most notable climate-related changes worldwide in 2003 were droughts in Southern Africa, heatwaves in India and floods in parts of South America.

Emmerich clearly feels that Americans are unlikely to care unless the violent weather conditions are personally aimed at them. He’s probably right. And it is no bad thing for more people to be reminded that the generally benign climate of our planet is not to be taken for granted.

But there must be a danger that when ordinary Americans discover that his doomsday scenario for the US is bogus, they will leap to the conclusion that there is nothing to worry about.

Politically, too, the film is nonsense. Emmerich repeats the fashionably liberal mantra of blaming the Bush administration for opposing the Kyoto agreement on climate change.

However, he does nothing to combat the Republican assertion that implementing Kyoto would cost at least $150 billion each year, and would do no more than delay global warming by a tiny period. On the environmentalists’ own figures, a degree of warming achieved in 2100 would merely be delayed by Kyoto to 2106.

For the same capital outlay, clean drinking water and sanitation could be provided within a year to everyone on the planet. Which is the more worthwhile use of money? Emmerich seems to have no doubts, but then someone building an underground sewage system in an unpronounceable village in Africa is a lot less cinematic than a 100-foot tidal wave engulfing the Empire State Building.

Capitalism constantly gets a raw deal from Hollywood – an irony, in view of the fact that moviemaking in the US is probably the most ruthlessly cut-throat business there is. The truth, largely unacknowledged by Hollywood lefties and European Greens alike, is that capitalism has conquered many kinds of disease, generated vast amounts of wealth and technology, and brought a quality of life that would never have been achieved under any other system. It’s even brought us some great movies.

Emmerich and those he is attempting to frighten need to understand that there is nothing inherently wrong with economic progress or making profits. There is plenty wrong with spreading a lot of irresponsibly alarmist lies about climate change.